YAZ is a programmers toolkit supporting the development of
Z39.50/SRW/SRU clients and servers. Z39.50-2003 (version 3) as well as
SRW/SRU version 1.1 are supported in both the client and server roles.

The current version of YAZ includes support for the industry standard
ZOOM API for Z39.50. This API vastly simplifies the process of writing
new clients using YAZ, and it reduces your dependency on any single
toolkit.
